1. Field of the Invention
This invention relates to a method of manufacturing a vent element, particularly an element having vent pores extending therethrough in parallel with the axial direction and having a comparatively uniform pore diameter, such as a vent for use in metal casting, die casting and rubber and plastic molding, a wear-resistant seat element, metering and supplying a liquid and a heat exchanger element.
2. Description of the Prior Art
There have hitherto been known many methods of manufacturing this kind of vent element, such as methods of drill machining, laser working, electro spark working, bundling and integrating metal tubes or sintering and infiltrating wire rods positioned in a compacted powder.
The methods of drill machining, laser working or electro spark working, however, are limited in thickness of the vent element and require a large amount of machining cost for forming a number of pores so that these methods are impractical. In the method of bundling metal tubes, the pore ratio is remarkably large if special thick tubes are not used, so that this method is limited in use. This bundling method also proposes to fill the interspaces between the tubes with an infiltrated metal or the like, but it is extremely difficult to manufacture it in practice. Besides, the sintering and infiltrating method can adjust a pore diameter and its ratio by selecting the outer diameter and the number of wire rod to be used, but requires large scale facilities for uniformly distributing and arranging wire rods, and the pore ratio becomes lessened.